Cyclooxygenase 2 in Gastric Carcinoma Is Expressed in Doublecortin- and CaM Kinase-Like-1-Positive Tuft Cells

Background/Aims: Doublecortin and CaM kinase-like-1 (DCAMKL1) is a marker of stem cells expressed predominantly in the crypt base in the intestine. However, DCAMKL1- positive cells have been shown to be differentiated tuft cells rather than quiescent progenitors. Tuft cells are the only epithelial cells that express cyclooxygenase 2 (COX-2) in the normal intestinal epithelium. We previously generated Cdx2- transgenic mice as model mice for intestinal metaplasia and gastric carcinoma. In the current study, we investigated the association between COX-2 and DCAMKL1 in gastric carcinoma. Methods: We examined the association between COX- 2 and DCAMKL1 expression in gastric carcinomas in clinical samples (early gastric well-differentiated adenocarcinoma) and Cdx2-transgenic mice; and the DCAMKL1-transgenic mouse stomach using immunohistochemistry and quantitative real-time polymerase chain reaction. Results: The COX- 2-expressing cells were scattered, not diffusely expressed, in gastric carcinomas from humans and Cdx2-transgenic mice. DCAMKL1-positive cells were also scattered in the gastric carcinomas, indicating that tuft cells could still be present in gastric carcinoma. COX-2 was expressed in DCAMKL1- positive tuft cells in Cdx2- and DCAMKL1-transgenic mouse stomachs, whereas the Sox9 transcription factor was ubiquitously expressed in gastric carcinomas, including COX-2- positive cells. Conclusions: COX-2 is expressed in DCAMKL1- expressing quiescent tuft cells in gastric carcinoma. (Gut Liver 2014;8:508-518)